1. Field of the Invention
The invention relates to the manufacture and use of functionalized polymers that can interact with fillers.
2. Background of the Invention
Rubber goods such as tire treads often are made from elastomeric compositions that contain one or more reinforcing materials such as, for example, particulate carbon black and silica; see, e.g., The Vanderbilt Rubber Handbook, 13th ed. (1990), pp. 603-04.
Good traction and resistance to abrasion are primary considerations for tire treads; however, motor vehicle fuel efficiency concerns argue for a minimization in their rolling resistance, which correlates with a reduction in hysteresis and heat build-up during operation of the tire. These considerations are, to a great extent, competing and somewhat contradictory: treads made from compositions designed to provide good road traction usually exhibit increased rolling resistance and vice versa.
Filler(s), polymer(s), and additives typically are chosen so as to provide an acceptable compromise or balance of these properties. Ensuring that reinforcing filler(s) are well dispersed throughout the elastomeric material(s) both enhances processability and acts to improve physical properties. Dispersion of fillers can be improved by increasing their interaction with the elastomer(s). Examples of efforts of this type include high temperature mixing in the presence of selectively reactive promoters, surface oxidation of compounding materials, surface grafting, and chemical modifications to the terminal ends of the polymers.
Where an elastomer is made by anionic polymerization techniques, attachment of certain functional groups is difficult. Living polymers are terminated by active hydrogen atoms such as are present in, e.g., primary and secondary amine groups.
Because amine functional groups provide desirable interaction with particulate fillers, particularly carbon black, a commercially useful method of providing living polymers with terminal amine functionality remains highly desirable. Because the interactivity with fillers tends to increase as the number of hydrogens bonded to the amino nitrogen increases, the provision of secondary and primary amine-functionality is particularly desirable.